Abstract

Summary

1.
R. akari was transmitted rectally and intracoelomically to the body louse by inoculation with peritoneal exudate of mice. In both cases the rickettsiae developed regularly and intensively in the louse. The same result was obtained when the lice were injected rectally with the blood of sick mice.

2.
Multiplication of the rickettsiae was always intracellular in the stomach wall, localized particularly in the basal part of the epithelial cell; it was extracellular in the coelom liquid, from which the organisms in rare cases entered the stomach cells as well.

3.
Multiplication of the rickettsiae in the stomach cells was moderate and did not deform them or cause the premature death of the louse; in the coelom, however, intense multiplication soon produced damage from which the louse died in a few days.

4.
After rectal inoculation the rickettsiae invade and destroy or detach some of the stomach cells. Through the partially damaged walls they may escape into the lumen of the stomach on one side and appear in the feces, or less frequently into the coelom on the other, and by intense multiplication cause the rapid death of the louse.

5.
By rectal transmission of ground stomach or coelom liquid of positive lice, R. akari can be maintained by serial passage in lice without losing virulence and pathogenicity for the mouse. The feces of the lice also contain virulent rickettsiae.

6.
The behavior of R. akari in the louse can best be explained by its close relationship to other rickettsiae, if we suppose that the capacity to develop in arthropods is a fundamental characteristic of all rickettsiae and that the different species of rickettsiae all have a common origin.